The Thunder series is somewhat tunable , the rear air door is on a spring so you can adjust the opening rate , to do this with the AFB you have to get out your drill & remove metal from the counterweight , I hope you do not remove to much or you will have to add a screw in the hole or weld it back up , the factory mostly used the Thunder type carbs not the AFB type , the factory also used the 800 cfm Thermo Quad on the 340 so yes I feel this would be a better choice than the AFB type of any size .
